Diesel fuel compositions

Abstract

A water-in-fuel emulsion composition containing a Fischer-Tropsch derived fuel and water, and its use in a compression ignition engine is provided. Emissions, for example of NO x , black smoke and/or particulate matter, are lower as compared to conventional fuels but without lengthening the ignition delay and reducing the cetane number. This is achieved without the need for, or at reduced levels of, ignition improving additives, and without engine modifications.

1. A water-in-fuel emulsion composition comprising a Fischer-Tropsch derived fuel and water, wherein said water-in-fuel emulsion composition has an ignition delay of equal or less than the equivalent cetane number of 40. 
     
     
       2. The composition of  claim 1  which contains no ignition improving additive. 
     
     
       3. The composition of  claim 1  wherein the water-in-fuel emulsion composition comprises an emulsifier. 
     
     
       4. The composition of  claim 1  wherein the water-in-fuel emulsion composition has an ignition delay of equal or less than the equivalent cetane number of about 44. 
     
     
       5. The composition of  claim 4  wherein the water-in-fuel emulsion composition has an ignition delay of equal or less than the equivalent cetane number of about 50. 
     
     
       6. A water-in-fuel emulsion composition comprising a Fischer-Tropsch derived fuel and water, wherein said water-in-fuel emulsion composition has an ignition delay of about 3 degrees of crank angle or less measured using an AVL/LEF 5312 engine wherein the operating conditions comprise a torque set point of 130 Nm, a speed set point of 1200 rpm, a coolant temperature set point of 80° C., an air intake temperature of 35° C., an air intake pressure of 140 kPa, an exhaust pressure of 120 kPa, and injection timing set at 1° of crank angle before top dead center (BTCD). 
     
     
       7. The composition of  claim 6  wherein the water-in-fuel emulsion composition has an ignition delay of about 3.1 degrees of crank angle or less. 
     
     
       8. The composition of  claim 6  which contains no ignition improving additive. 
     
     
       9. The composition of  claim 7  which contains no ignition improving. additive. 
     
     
       10. The composition of  claim 6  wherein the water-in-fuel emulsion composition comprises an emulsifier. 
     
     
       11. The composition of  claim 7  wherein the water-in-fuel emulsion composition comprises an emulsifier. 
     
     
       12. A method of reducing ignition delay in a compression ignition engine comprising operating the compression ignition engine in the presence of a water-in-fuel emulsion composition, said composition comprising a Fischer-Tropsch produced fuel and water. 
     
     
       13. A method of reducing the emission of NOx from a compression ignition engine comprising operating the compression ignition engine in the presence of a water-in-fuel emulsion composition, said composition comprising a Fischer-Tropsch produced fuel and water. 
     
     
       14. A method of reducing the emission of black smoke and/or particulate matter from a compression ignition engine comprising operating the compression ignition engine in the presence of a water-in-fuel emulsion composition, said composition comprising a Fischer-Tropsch derived fuel and water. 
     
     
       15. The method of  claim 12  wherein the water-in-fuel emulsion composition contains no ignition-improving additive. 
     
     
       16. The method of  claim 13  wherein the water-in-fuel emulsion composition contains no ignition-improving additive. 
     
     
       17. The method of  claim 14  wherein the water-in-fuel emulsion composition contains no ignition-improving additive. 
     
     
       18. A method of reducing emissions of NO X  and/or black smoke and/or particulate matter in a compression ignition engine, as compared to that when using a conventional fuel having a specification in accordance with ASTM D975, but without reducing the ignition quality, which comprises replacing said fuel in said engine by a water-in-fuel emulsion composition which comprises a Fischer-Tropsch derived fuel and water. 
     
     
       19. A method of operating a compression ignition engine comprising including in said engine a water-in-fuel emulsion composition which comprises a Fischer-Tropsch derived fuel and water. 
     
     
       20. The method of  claim 19  wherein the water-in-fuel emulsion composition has an ignition delay of about 3 degrees of crank angle or less measured using an AVL/LEF 5312 engine wherein the operating conditions comprise a torque set point of 130 Nm, a speed set point of 1200 rpm, a coolant temperature set point of 80° C., an air intake temperature of 35° C., an air intake pressure of 140 kPa, an exhaust pressure of 120 kPa, and injection timing set at 1° of crank angle BTCD. 
     
     
       21. The method of  claim 19  wherein the water-in-fuel emulsion composition has an ignition delay of equal or less than the equivalent cetane number of 40. 
     
     
       22. The method of  claim 20  wherein the water-in-fuel emulsion composition has an ignition delay of about 3.1 degrees of crank an angle or less. 
     
     
       23. The method of  claim 21  wherein the water-in-fuel emulsion composition has an ignition delay of equal or less than the equivalent cetane number of about 44. 
     
     
       24. The method of  claim 20  which contains no ignition improving additive. 
     
     
       25. The method of  claim 21  which contains no ignition improving additive. 
     
     
       26. The method of  claim 22  which contains no ignition improving additive. 
     
     
       27. The method of  claim 23  which contains no ignition improving additive. 
     
     
       28. A process for the preparation of a water-in-fuel emulsion composition which process comprises admixing a Fischer-Tropsch derived fuel with water.